Our invention relates to sampling apparatus, and more specifically to apparatus for taking samples from a continuous stream of printed sheets to enable the inspector to see if they are printed or folded properly or to check them for other inspection items. Still more specifically, our invention is directed to such sampling apparatus particularly well adaptable for use with a web-fed rotary press, for sampling sets or "signatures" of printed and folded sheets as they are delivered from the folder to the counter-stacker of the press, among other applications.
Heretofore, the sampling of sets of printed and folded sheets travelling at high speed in a continuous, overlapping row from the folder to the counter-stacker of a rotary press has usually been the manual job of skilled inspectors. The manual sampling operation is so difficult, however, that the inspectors have inevitably often disarranged the row of printed sheet sets during extraction of samples therefrom, resulting in the trouble of the counter-stacker or other subsequent equipment.
We are aware of a device already proposed and used for automatically withdrawing damaged or otherwise faulty printed sheets from a continuous stream of such sheets. This prior art device is not suitable for sampling operation, however, since the device withdraws at least seven or so sheets or sets of sheets at one time, compared with about two ordinarily required for inspection purposes.